1. Field of the Invention
The present invention relates to a device for repeatedly injecting dosages of a liquid medicament from a container for liquids, especially a carpule (=injection ampoule), equipped with a piston, said container being attachable to or detachable from a manually drivable transmission incorporated into a transmission sleeve, said transmission comprising a drive member comprised of a guide button and a carrier sleeve firmly attached thereto, said drive member being disposed rotatably and shiftably in the advance direction of the piston in the transmission sleeve, a driven member comprised of a threaded rod and a flange, said driven member being shiftable in the advance direction of the piston and being carriable over a certain distance under the influence of the drive member executing longitudinal shifts, a transmission element being screwably disposed on the threaded rod and having the effect of the driven member being carried along by the drive member, a compression spring acting between the transmission sleeve and the carrier sleeve, in which the drive member is lockable by a locking device, the threaded rod of the driven member is disposed nonrotatably and shiftable in the longitudinal direction in the transmission sleeve, and the transmission element is rotatable but attached shiftably in the longitudinal direction to the drive member.
2. Description of the Prior Art
Such injection devices have been known for some time, for example a device described in EP-0 245 312 B1 which must be regarded as the closest prior art. It has the purpose of injecting respectively selectable amounts of liquid from a container for liquids equipped with a piston, especially a carpule (=injection ampoule).
Said carpule in a carpule holder is attachable to or detachable from a manually drivable transmission. The transmission is incorporated into a transmission sleeve. In addition to other parts, it comprises
a drive member comprised of a guide button and a carrier sleeve firmly attached thereto, said drive member being disposed rotatably and shiftably in the advance direction of the piston in the transmission sleeve, PA1 a driven member comprised of a threaded rod and a flange, said driven member being shiftable in the advance direction of the piston and being carriable over a certain distance under the influence of the drive member executing longitudinal shifts, PA1 a transmission element being screwably disposed on the threaded rod, PA1 a compression spring acting between the transmission sleeve and the carrier sleeve. PA1 a home position, where the drive member is at its furthest possible distance from the piston and the transmission element is close to the piston, PA1 an intermediate position where the drive member remains in its position, but the transmission element, depending on the amount of liquid to be injected, is further away from the piston than in its home position, PA1 a final position where the drive member is closer to the piston and the driven member has protruded further from the transmission than in the home or intermediate position and has penetrated into the carpule which causes injection of the selected amount of liquid.
While being operated, the injection device may be in the following positions:
The final position reverts to the home position by itself.
The transmission is not locked in any of the three positions so that it may be exposed to influences during storage or transport of the injection device which may cause a change in the amount of liquid in the carpule or even permit the entry of air into the carpule. In addition, it has many components, some of which are not very easy to manufacture.